Searing summer heat will continue through Wednesday as most of Connecticut endures its third heat wave of the summer. Temperatures will soar to between 10 and 15 degrees above average, but the high humidity accompanying these torrid temperatures will make this heat hazardous.

The next few days will add to some already long streaks of above-average temperatures, according to the National Weather Service. New Haven will experience its 17th day in a row with above-average temperatures today. The Hartford area will have its 13th straight above-average day. Danbury and Bridgeport will see their 12th consecutive day with above-average temperatures.

What makes the heat this week so dangerous is the heat index values. The heat index is what it feels like when both temperature and humidity are considered. The National Weather Service and the Centers for Disease Control and Prevention began implementing the new HeatRisk tool this year that helps to assess the heat-related impacts on our health.

The heat should peak on Tuesday for most areas. Most of the state will be in the major HeatRisk category, or level three out of four. Interior portions of the state and inland areas from Stamford to Bridgeport will be in the extreme category, level four out of four. The National Weather Service says that at that level, the risk of heat-related impacts is extreme, and “this level of rare and/or long-duration extreme heat with little to no overnight relief affects anyone without effective cooling and/or adequate hydration. Impacts likely in most health systems, heat-sensitive industries and infrastructure.”

A heat advisory is in effect today from 8 a.m. to 8 p.m. for Hartford, Tolland and Windham Counties.

Heat advisories are also in effect from noon Monday through 10 p.m. Tuesday for Fairfield, New Haven and Middlesex Counties, and the inland portions of New London County. An excessive heat watch has also been issued for Hartford, Tolland and Windham Counties from Tuesday morning through Tuesday evening.

“Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun and check up on relatives and neighbors,” advises the National Weather Service. “Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.”

A cold front late Wednesday into Thursday will bring a break from the oppressive, but possibly at a cost.

The front will spark showers and thunderstorms, which will be fueled by the extreme heat and humidity. This raises the risk that the storms could grow to severe limits. Hazards from any severe storms that may develop will be mainly damaging winds and large hail, but even a few tornadoes can’t be ruled out.

Any showers and thunderstorms that do develop could lay down torrential amounts of rain. The Weather Prediction Center’s excessive rainfall outlook for Thursday has most of New England at a marginal risk, level one out of four, for heavy rainfall to produce flash flooding.

The relief that comes in the wake of Wednesday’s storms should last through the end of the weekend, and at least through the start of next weekend. Temperatures should drop to more seasonable levels for the middle of summer. Average highs for this time of the year are in the lower to middle 80s.

The Climate Prediction Center’s 6-10 day temperature outlook suggests temperatures could climb back above average again fairly soon. The forecast has the state “leaning above” average overall for the period that includes next weekend and the following Monday, Tuesday and Wednesday.

Connecticut weather forecast

Today

Inland: Sun and cloud mix, isolated p.m. shower or thunderstorm possible, hot, highs in the middle 90s.

Shoreline: Partly to mostly sunny, scattered p.m. shower or thunderstorm possible, highs near 90.

Tonight

Inland: Scattered showers and thunderstorms possible, partly cloudy, muggy, lows in the lower 70s.

Shoreline: Scattered shower or thunderstorm possible early, then partly cloudy, lows in the lower 70s.

Tuesday

Inland: Partly to mostly sunny, very hot, humid, p.m. scattered thunderstorm possible, highs in the upper 90s.

Shoreline: Mostly sunny, hot and humid, p.m. isolated thunderstorm possible, highs in the middle 90s.

Tuesday night

Inland: Scattered showers and thunderstorms possible, partly cloudy, lows in the lower 70s.

Shoreline: Partly cloudy, warm and muggy, lows in the middle 70s.

Wednesday

Inland: Partly to mostly cloudy, mainly afternoon scattered showers and thunderstorms, locally heavy rainfall possible, highs in the middle 90s.

Shoreline: Mostly sunny start, then showers and thunderstorms develop in the afternoon, highs near 90.

Thursday

Inland: Shower possible early, then partly to mostly sunny, highs in the middle 80s.

Shoreline: Morning shower or thunderstorm possible, then a mix of sun and clouds, highs in the middle 80s.

Friday

Inland: Mostly sunny, highs in the middle 80s.

Shoreline: Mostly sunny, highs in the lower to middle 80s.

Saturday

Inland: Mostly sunny, highs in the middle to upper 80s.

Shoreline: Mostly sunny, highs in the middle 80s.

Sunday

Inland: Mostly cloudy, scattered showers and thunderstorms, highs in the middle 80s.

Shoreline: Mostly cloudy, scattered showers and thunderstorms, highs near 80.